How It Works

 

As shown below, an arrow (yellow) attached to rotating disc (driven by a stepper motor) protrudes above the disc's surface. 12 posts (yellow), protruding the same height as the arrow, surround the disc and mark the hours. The entire clock face is covered with a thin, flexible opaque latex membrane (gray) that is tightly stretched to create a smooth appearance.  When a small vacuum is applied the latex is pulled downwards and it conforms to the shapes of the arrow and dots. The vacuum is activated by a motion sensor and when applied the stepper motor may need to pause in order to prevent damage to the gears and the latex. When the vacuum is slowly released the latex gradually returns to it's un-deformed condition and the motor, if needed, will be programmed to restart and catch up for lost time. 

 

A vacuum reserve will store the vacuum so that the pump will not need to turn on in response to activation of the motion sensor. A solenoid valve connected to the vacuum reserve will open when the clock is activated. To return the membrane to it's un-stretched form the solenoid will close and another solenoid will open in order to gradually relieve the vacuum. The vacuum pump will periodically turn on to restore the reserve's vacuum.